1. Field of the Invention
The present invention relates to an apparatus for encoding video signals used for a teleconference or videophone.
2. Description of the Related Art
Video signal encoding systems have more positively been studied in recent years because they will be standardized soon. Also, intelligent encoding has been proposed as a future encoding system and encoding systems using knowledge of image in any form have been discussed as part of the study. As one of the encoding systems, the system is proposed to detect facial region from motion picture signals of human image and distribute many quantizing bit number to image signals of facial region.
For example, in the Preture Coding symposium Japan PCSJ89, 7-15 in 1989, the technique was disclosed to relatively improve the quality of decoded images of facial region by making the quantizing step size of regions other than facial region larger than the quantizing step size determined by the capacity of the buffer to store encoded data when quantizing DCT (Discrete Cosine Transform) coefficient obtained by DCT-encoding movement images. This technique, however, has the problem that visually-remarkably distortion peculiar to DCT-encoding such as block distortion is generated in decoded image because there are many quantization noise of DCT coefficient in regions other than facial region.